Roast potatoes will be 'extra crunchy' when you use 1 ingredient Mary Berry loves

Everyone wants the perfect roast potato with a crunchy exterior, but this can be hard to achieve. Common mistakes include not fluffing them up before going into the oven and not heating the oil in the pan. Luckily, Mary Berry, who has shared a plethora of potato recipes throughout her career, has shared her foolproof roastie recipe.

The recipe notes said: "A roast potato should be ultra crispy and golden on the outside with a fluffy light middle. Par-boiling and roughing them up before roasting gives a lovely crunchy exterior, and the semolina adds an extra crunchy coating."

Ingredients:

1.5kg old potatoes, peeled and cut into medium-sized cubes

40g semolina

Four tablespoons of goose fat or vegetable oil

Three thyme sprigs

Salt

Method:

Preheat the oven to 220°C or 200°C Fan and then put the potatoes in a saucepan of cold salted water.

Bring to a boil for about five minutes, until starting to soften around the edges.

Drain in a colander until completely dry, then put back into the saucepan and shake to roughen up the edges. Sprinkle the semolina and shake until coated.

Semolina, made from durum wheat, has a coarse, gritty texture. When sprinkled on parboiled potatoes, the rough grains stick to them, which crisp up in the oven.

It's available to buy from most supermarkets and is well worth using if you want to impress guests.

Preheat a large shallow roasting tin in the oven until hot. Add the fat to the tin and heat for five minutes until smoking. Carefully add the potatoes, turn in the fat until coated and scatter over the thyme.

Return to the oven for about 45 to 55 minutes until golden brown and crisp, making sure to turn the potatoes halfway through cooking. Serve piping hot with your roast dinner.